Nephrotic range proteinuria in a renal transplant associated with oncocytoma of the native kidney

Membranous glomerulonephritis (MGN) is known to cause post-transplant nephrotic syndrome and may be recurrent or de novo [1,2]. Focal glomerulosclerosis (FGS) may also present with nephrotic range proteinuria and has a high incidence of recurrence posttransplantation (20–40%) and approximately half of these recurrences may lead to allograft failure. The risk of recurrent MGN has been reported to be 29% at 3 years and it appears to be more common than de novo MGN in transplant recipients [2,3]. Schwartz et al. [2] have reported that de novoMGNmay occur in 5.3% of patients at 8 years. Although nephrotic syndrome is known to complicate underlying malignancies in the non-transplant setting, the association between nephrotic range proteinuria and tumours following renal transplantation is less well defined. This case report addresses the possible mechanisms of proteinuria in a patient with simultaneous recurrent FGS and de novo MGN in a renal transplant. The report describes the association between the removal of an oncocytoma and the complete reversal of nephrotic range proteinuria, likely to relate to MGN, suggesting that this tumour was the underlying immunological stimulus for the proteinuria.